ES2604256T3 - Procedure for obtaining allyl methacrylate - Google Patents

Abstract

Process for obtaining allyl methacrylate, which comprises the reaction of allyl alcohol with a methacrylic acid ester, characterized in that the reaction is catalyzed by zirconium acetylacetonate.

Description

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description

Procedure for obtaining allyl methacrylate

The present invention relates to processes for obtaining allyl methacrylate.

Allyl methacrylate serves, among other things, as an intermediate for obtaining methacrylates containing silyl groups. Accordingly, multiple methods for obtaining this compound are known. These include, in particular, processes in which allyl alcohol is reacted with methacrylates, for example, methyl methacrylate or ethyl methacrylate. Different catalysts can be used to improve the performance and selectivity of the reaction.

By way of example, acid bases may be used to catalyze the transesterification. Such reactions are presented, by way of example, in documents CN 1410412 or DE 34 23 441. However, in the case of using these catalysts, side reactions must be available, such as the addition of Michael, which reduces both the purity of the desired allyl methacrylate, as well as the yield.

According to JP 11222461, the transesterification of methyl methacrylate with allyl alcohol can be catalyzed by titanium alcoholates. However, in particular, nitrogenous polymerization inhibitors are employed which, however, are undesirable in allyl methacrylate.

JP-01-258642 describes the reaction of methyl methacrylate with allyl alcohol in the presence of titanium catalysts. In this case, nitrogen polymerization inhibitors are used.

Document DE 28 05 702 further describes the obtaining of esters of unsaturated carboxylic acids. In order to catalyze the described reactions, compounds containing zirconium and / or calcium may be used in particular. Especially suitable catalysts belong especially zirconium acetylacetonate. However, obtaining allyl methacrylate is not explicitly described. The reactions lead to high yields of approximately 98%, based on the alcohol used. However, it follows that the product contains considerable quantities of secondary products.

Obtaining methacrylates containing silyl groups from allyl alcohol requires a very high purity of educts, since impurities, for example allyl alcohol and water, can deactivate the Pt catalyst used for silane methacrylate synthesis. Secondary nitrogen components interfere in the same way. Therefore, allyl methacrylate, which is distributed commercially as an educt for these purposes, must contain at most 200 ppm of allyl alcohol, being as small as possible an atypical alcohol content. To meet these requirements, the products obtained according to the state of the art must be purified in a complicated manner.

Considering the state of the art, the task of the present invention was now to make available a process for obtaining allyl methacrylate, in which the product was obtained with a very high purity. The allyl methacrylate obtained should contain only very small amounts of allyl alcohol and / or water.

Another task of the invention was to create a process in which allyl methacrylate could be obtained very selectively.

In addition, it was the task of the present invention to make available procedures for obtaining allyl methacrylate, which could be carried out in a simple and economical manner. In this case, the product should be obtained in yields as high as possible and, considered in short, low energy consumption. In addition, the reaction should be carried out in particular without ritrogenating polymerization inhibitors.

These, like other tasks not explicitly cited, but which can be derived or deduced without further ado from the context discussed here in an introductory manner, are solved by procedures with all the features of claim 1. In the dependent claims, referred to claim 1, convenient modifications of the method according to the invention are protected.

Accordingly, it is the object of the present invention a process for obtaining allo methacrylate, which comprises the reaction of allyl alcohol with a methacrylic acid ester, the reaction being catalyzed by zirconium acetylacetonate.

Thus, in an unpredictable way, it is possible to make available a process for obtaining allyl methacrylate, in which the product is obtained with a very high purity. Surprisingly, the

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product obtained contains only very small amounts of allyl alcohol and / or water.

Moreover, the process according to the invention enables an especially selective allyl methacrylate obteroion.

In addition, the process according to the invention can be carried out in a simple and economical manner, the product being able to be obtained in high yields and, considered in short, low energy consumption. In addition, the reaction can be carried out especially without nitrogenous polymerization inhibitors.

According to the invention, allyl methacrylate is obtained. Allyl methacrylate (propenyl 2-methylpropenate) has long been known, and has CAS number 96-05-9.

For the production of allyl methacrylate, according to the invention, alkoxy alcohol (2-propen-1-ol) is used, which is commercially available from Lyondell. The CAS number of alcoholic alcohol is 10718-6.

According to the present invention, alcoholic alcohol is reacted with a methacrylic acid ester. Especially suitable methacrylates are formed, especially from alcohols with 1 to 4 carbon atoms. These include, in particular, methanol, ethanol, n-propanol, i-propanol, n-butanol and tert-butanol. Especially preferably, ethyl methacrylate or methyl methacrylate is especially used, with methyl methacrylate being particularly preferred.

The weight ratio of alcoholic alcohol with respect to methacrylic acid ester is preferably in the range of 1: 1.5 to 1: 10, particularly preferably 1: 2.5 to 1: 5, and very particularly preferably in The 1: 3 to 1: 4 range. Too much excess ester can reduce the reaction rate, too high excess is not economically reasonable, since it reduces the volume of useful boiler.

According to the invention, zirconium acetylacetonate is used for the catalysis of the present invention. The CAS number of zirconium acetylacetonate is 17501-44-9. Obtaining zirconium acetylacetonate from acetylacetone (pentane-2,4-dione) and zirconium compounds is described, for example, in Houben-Weyl, Methoder der orgarisoher Chemie, 4th edioion, volume VI / 2, 1963 , pages 53-55 and 58 to 61, as well as AE Martell, M. Calvin, "Die Chemie der Metallohelatverbindungen" (1958). You can use 0.2 to 5 mmol, especially preferably 0.5 to 2 mmol of zirconium acetylacetonate per mole of alflioo alcohol. The obtaining of the catalyst can also be carried out on site, adding the starting materials before or during the transesterification of the reaction mixture.

The reaction can be carried out in overpressure or ford. Depending on the variability, especially the present invention, the transverse esterification can be carried out at a pressure in the range of 200 to 2000 mbar, especially preferably in the range of 500 to 1300 mbar.

The reaction temperature can also be located in a wide range, especially depending on the previous one. According to the preferred form of the present invention, the reaction is preferably carried out at a temperature in the range of 80 ° C to 120 ° C, especially preferably 95 to 1150 ° C.

Surprisingly, special advantages can be obtained if the temperature at which the reaction is effected increases in the course of the reaction. According to this preferred variation of the process according to the invention, the temperature at the beginning of the reaction, especially up to a conversion of 80%, preferably up to a conversion of 70%, based on the weight of alcohol used, can preferably be placed in the range from 90oc to 100oc, and after the end of the reaction, especially after an 80% conversion, preferably after a 90% conversion, based on the weight of alflioo alcohol used, can be placed in the 105oc range at 115oc.

The transesterifioaoion can be carried out both on an ongoing basis, or also by oargas. It is also possible not to have a part of methacrylate used for the transesterifioaoion already before the beginning of the reaction, but to add the dose with the same only during the reaction. The process according to the invention can be carried out in substance, that is, without the use of an additional solvent. In desired case, an inert solvent can also be used. These include, among others, benoin, benoeno, toluene, n-hexane, oiolohexane and methyl isobutyl ketone (MIBK), methyl ethyl ketone (MEK).

In a particularly convenient variant of the process according to the invention, all components are mixed, such as, for example, allyl alcohol, methacrylate, as well as the catalyst, after which this reaction mixture is boiled until boiling. In this case, water is first separated, which can be contained in the alcohol, by azeotropy with the methane acid ester. On oontinuaoion, the alcohol that is released can be

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remove from the reaction mixture by distillation, for example, methanol or ethanol, if necessary by azeotropic with methyl methacrylate or ethyl methacrylate.

According to a special variation of the present reaction, the fraction of water in the allyl methacrylate preferably amounts to a maximum of 0.1%, especially preferably a maximum of 0.02% by weight, based on the weight of the composition.

The reaction times are dependent, among other things, on the selected parameters, such as pressure and temperature. However, these are generally in the range of 1 to 24 hours, preferably 3 to 12 hours, and most particularly preferably 6 to 9 hours. In continuous procedures, residence times are generally in the range of 0.5 to 24 hours, preferably 1 to 12 hours, and most particularly preferably 2 to 3 hours. The specialist can extract from the attached examples other references regarding reaction times.

The reaction can preferably take place under stirring, the stirring speed being particularly preferably in the range of 50 to 2000 rpm, very particularly preferably in the range of 100 to 500 rpm.

The pH value can be placed in a wide range. The reaction can be conveniently carried out at a pH value in the range of 5 to 9, preferably 6 to 8.

To prevent unwanted methacrylate polymerization, polymerization inhibitors can be used in the reaction. These compounds, such as hydroquinones, hydroquinone ethers, such as hydroquinone monomethyl ether or di-tert-butylbrenzocatechin, phenothiazine, p-phenylenediamine, methylene blue, or phenols with steric hindrance, are widely known in the technical world. These compounds can be used separately or in the form of mixtures, and are generally commercially available. The action of the stabilizers is almost always that they act as radical scavengers for the free radicals that occur in the polymerization. For more details, refer to the common technical literature, especially Rompp-Lexikon Chemie; editor: J. Falbe, M. Regitz; Stuttgart, New York; 10th edition (1996); keyword "antioxidants", and the bibliographic citations indicated in this point.

Among others, polymerization inhibitors that do not contain nitrogen are especially suitable. Phenols are preferably used as a polymerization inhibitor. Especially surprising advantages can be obtained with the use of mixtures comprising hydroquinone and hydroquinone monomethyl ether. Regarding the weight of the total reaction mixture, the fraction of isolated inhibitors or as a mixture can generally amount to 0.01-0.5% (wt / wt). In this case it is convenient to load not only the reaction tank, but also the column, and if necessary the condenser areas, with inhibitors that can be dosed, for example, in the reflux of the column.

Moreover, oxygen can be used for inhibition. In this case, it can be used, for example, in the form of air, the amounts being dosed advantageously so that the content in the gas phase on the reaction mixture remains below the explosion kmite. In this case, amounts of air in the range of 0.05 to 0.5 L per hour and mole of allyl alcohol are especially preferred. In the case of discontinuous procedures, this amount may refer to the amount of alflic alcohol originally used. In continuous procedures, this amount may refer to the amount of alflic alcohol fed. Similarly, mixtures of inert-oxygen gas, for example nitrogen-oxygen, argon-oxygen, or carbon dioxide-oxygen can be used.

According to a special conditioning of the present invention, a combination of oxygen with at least one phenol, preferably hydroquinone and / or hydroquinone monomethyl ether, can be used for inhibition.

Corresponding to a convenient embodiment of the present invention, the alcohol released from the methacrylate employed, by way of example methanol and / or ethanol, can be separated by distillation. In this case, a mixture containing methyl methacrylate and methanol can be advantageously separated by way of example. Surprisingly, a part of the separated mixture can be advantageously returned to the next load. According to this variation, the separable separable mixture fraction can be obtained at the end of the reaction, especially after an 80% conversion, preferably after a 90% conversion of the allyl alcohol used. By way of example, the mixture fraction returned at the beginning of the next load can be in the range of 40 to 60%, based on the total methacrylate weight to be transesterified.

In the case of discontinuous procedures, the excess educt, especially the non-transformed ester of methacrylic acid, can be separated by distillation towards the end of the reaction. It can also be used again in the next load without further purification. The distillate rich in methanol or ethanol obtained at the beginning of the reaction can also be recycled, by way of example by incorporation into an installation for

Obtaining transesterified methacrylate ester activated in combination.

An installation suitable for carrying out the present transesterification can comprise, by way of example, an agitation boiler reactor with stirring mechanism, steam heating, distillation column and condenser. Such installations are known in sf, and are described, by way of example, in Ullmanns 5 Encyclopedia of Industrial Chemistry (6th edition), Verlag Wiley-VCH, Weinheim 2003, volume 10, page 647. The size of the installation is dependent on the amount of allyl methacrylate to be obtained, the present process being able to be carried out both on a laboratory scale, as well as on an industrial scale. According to a special aspect, the stirring boiler reactor may correspondingly have a boiler volume in the range of 1m3 to 20 m3, preferably 3 m3 to 10 m3. The agitator mechanism of the reactor boiler may be specially configured in the form of an anchor, rotor, blade stirrer or inter-MIG agitator.

The task of the distillation column is to ensure that an azeotrope rich in methanol, or ethanol, is discharged to minimize the loss of educated esters concomitantly discharged.

The distillation column may have one, two or more separation stages. The number of theoretical stages is called the number of plates in a column of plates, or the number of theoretical separation stages in the case of a packing column, or a column with filling bodies. Examples of a multi-stage distillation column with plates include those such as bubble dishes, perforated plates, passing plates, valve plates, grooved plates, perforated-grooved plates, bubble-perforated plates, nozzle plates, centigrade plates , for a multi-stage distillation column with filling bodies those such as Raschig rings, Lessing rings, Pall rings, Berl saddles, Intalox saddles, and for a 20-stage distillation column with gaskets such as those of type Mellapak (Sulzer), Rombopak (Kuhni), Montz-Pak (Montz). By way of example in the case of the use of methyl methacrylate, by adapting the conversion-dependent reflux ratio, a fraction of methanol in the distillate that is above 60% over wide conversion intervals can be adjusted .

To the appropriate capacitors, which may be contained in the installation for the implementation of the present transesterification, belong, among others, plate and tube beam heat exchangers.

Upon completion of the reaction, the allyl methacrylate obtained already frequently meets the high requirements set forth above, so that in many cases no further purification is necessary. For additional quality increase, and especially for catalyst separation, the obtained mixture can be purified by known procedures. Due to the tendency to polymerize the monomers, 30 distillation procedures are recommended in which the thermal load of the substance to be distilled has been minimized. Devices in which the monomer evaporates continuously from a thin layer, such as gravity molecular evaporators and evaporators with a rotary cleaning system, are suitably suitable. Short-term evaporators can also be used. Such devices are known (Ullmanns Encyclopedia of Industrial Chemistry (6th edition), Verlag Wiley-VCH, Weinheim 2003, volume 36, page 505). By way of example, a distillation can be carried out in which a continuous evaporator with rotary cleaning system and superimposed column can be used. This distillation can be carried out, for example, at a pressure in the range of 40 to 60 mbar, and at an evaporator temperature of 1100C to 1300C.

Surprisingly, by means of the measures according to the invention it is possible to make available a process in which allyl methacrylate can be obtained, containing less than 0.04%, especially preferably less than 0.02%, and of very especially preferably less than 0.01% of allyl alcohol, based on the weight of the composition.

In the following, the present invention should be explained by means of comparative examples and examples, without limiting this way.

Comparative Example 1

45 In a 7m3 stirring boiler reactor with stirring mechanism, steam heating, distillation column and condenser, 850 kg of allyl alcohol, 4800 kg of methyl methacrylate (mMa), 0.68 kg of phenothiazine, asf as 0.22 kg of N-N'-diphenyl-p-phenylenediamine as inhibitors, and as catalyst 34 kg of lauryl titanate, and stirred under introduction of air. It is heated to 95 ° C tail temperature, the column being operated first under full reflux. As soon as the temperature at the head of the column falls below 700C 50, the methanol-MMA mixture is extracted under a reflux ratio of 1: 1. In the 8 h interval the reflux ratio is adjusted to up to 4, 5: 1 of the formation of descending methanol. The reaction has concluded at a tail temperature of 115oc, and excess MMA is extracted in vain, the pressure gradually reduced to 5 Torr. The ford is suppressed when it is no longer separated by MMA distillation. The boiler content consists of 1780 kg of allyl methacrylate, which still contains 4000 ppm of allyl alcohol and 1700 ppm of methyl methacrylate (determined by gas chromatography).

Comparative Example 2

In a 7m3 stirring boiler reactor with stirring mechanism, steam heating, distillation column and condenser, 1160 kg of akyl alcohol, 4800 kg of methyl methacrylate (MMA), 1.79 kg of hydroquinone are collected, as ^ as 0.34 kg of hydroquinone monomethylether as inhibitors, and as catalyst 34 kg of 5 lauryl titanate, and stirred under introduction of air. It is heated to 95 ° C tail temperature, the column being operated first under full reflux. As soon as the temperature at the head of the column falls below 70 ° C, the methanol-MMA mixture is extracted under a reflux ratio of 1: 1. In the 8 h interval the reflux ratio is adjusted to up to 4.5 : 1 of the formation of descending methanol. The reaction has concluded at a tail temperature of 115oc, and excess MMA is extracted in vain, gradually reducing the pressure 10 to 5 Torr. The ford is suppressed when it is no longer separated by MMA distillation. The boiler content consists of 25o0 kg of allyl methacrylate, which still contains 1200 ppm of allyl alcohol and 7400 ppm of methyl methacrylate (determined by gas chromatography).

Example 1

In a 7m3 stirring boiler reactor with stirring mechanism, steam heating, distillation column 15 and condenser, 1275 kg of allyl alcohol, 4800 kg of methyl methacrylate (MMA), 1.8 kg of hydroquinone, asf as 0.34 kg of hydroquinone monomethylether as inhibitors, and as a catalyst 7.7 kg of zirconium acetylacetonate, and stirred under air introduction. It is heated to 95 ° C tail temperature, the column being operated first under full reflux. As soon as the temperature at the head of the column falls below 70oc, the methanol-MMA mixture is extracted under a reflux ratio of 1: 1. In the 20 hour interval of 8 h the reflux ratio is adjusted to up to 4, 5: 1 of the formation of descending methanol. The reaction has concluded at a tail temperature of 115oc, and excess MMA is extracted in vain, the pressure gradually reduced to 5 Torr. The ford is suppressed when it is no longer separated by MMA distillation. The boiler content consists of 2500 kg of allyl methacrylate, which still contains 30 ppm of allyl alcohol and 4280 ppm of methyl methacrylate (determined by gas chromatography).

25 Example 2

In a 7m3 stirring boiler reactor with stirring mechanism, steam heating, distillation column and condenser, 1326 kg of allyl alcohol, 4800 kg of methyl methacrylate (MMA), 1.8 kg of hydroquinone are collected, as well as 0.34 kg of hydroquinone monomethyl ether as inhibitors, and as a catalyst 7.7 kg of zirconium acetylacetonate, and stirred under air introduction. It is heated to 95 ° C tail temperature, the column being operated first under full reflux. As soon as the temperature at the head of the column falls below 70oc, the methanol-MMA mixture is extracted under a reflux ratio of 1: 1. In the 8 h interval the reflux ratio is adjusted to up to 4.5 : 1 of the formation of descending methanol. The reaction has concluded at a tail temperature of 115oc, and excess MMA is extracted in vain, the pressure gradually reduced to 5 Torr. The ford is suppressed when it is no longer separated by MMA distillation. The content of the boiler is constituted by 2740 kg of allyl methacrylate, which still contains 10 ppm of afflic alcohol and 4120 ppm of methyl methacrylate (determined by gas chromatography).

Example 3

In a 7m3 stirring boiler reactor with stirring mechanism, steam heating, distillation column and condenser, 1340 kg of allyl alcohol, 4880 kg of methyl methacrylate (MMA), 1.8 kg of 40 hydroquinone, asf as 0.34 kg of hydroquinone monomethylether as inhibitors, and as a catalyst 7.7 kg of zirconium acetylacetonate, and stirred under air introduction. It is heated to 95 ° C tail temperature, the column being operated first under full reflux. As soon as the temperature at the head of the column falls below 70 ° C, the methanol-MMA mixture is extracted under a reflux ratio of 1: 1. Simultaneously 700 kg of MMA is dosed in the 4 h interval, with a speed at the charge corresponding to the amount of methanol-MMA discharged per time. In the 8 h interval, the reflux ratio is adapted to up to 4.5: 1 of the descending methanol formation. The reaction has concluded at a tail temperature of 117oc, and excess MMA is extracted in vain, the pressure gradually reduced to 5 Torr. The ford is suppressed when it is no longer separated by MMA distillation. The content of the boiler consists of 2680 kg of allyl methacrylate, which still contains 50 ppm of allyl alcohol and 1160 ppm of methyl methacrylate (determined 50 by gas chromatography).

Distillation purification of allyl methacrylate

In a continuous evaporator (area 3.5 m2) with rotary cleaning system and superimposed column, 450 kg / h of crude allyl methacrylate are fed at 50 mbar pressure and 120oc evaporator temperature. A temperature of 60oc is set at the head of the column. 425 kg / h of distillate consisting of pure allyl methacrylate is extracted, which is stabilized with 50 ppm of hydroquinone monomethyl ether for later storage.

Composition (determined by gas chromatography) a) Starting from the raw material of comparative example 2:

99.55% allyl methacrylate, 0.37% MMA, 0.033% allyl alcohol Water content (determined by Karl-Fischer titration): 350 ppm 5 b) Starting from the raw material of the inventive example 1:

99.71% allyl methacrylate, 0.22% MMA, 0.006% allyl alcohol Water content (determined by Karl-Fischer titration): 110 ppm c) Starting from the raw material of inventive example 3:

99.88% allyl methacrylate, 0.11% MMA, 0.005% allyl alcohol 10 Water content (determined by Karl-Fischer titration): 50 ppm

Claims (19)

5 10 fifteen twenty 25 30 35 claims 1. - Procedure for obtaining allyl methacrylate, which comprises the reaction of allyl alcohol with a methacrylic acid ester, characterized in that the reaction is catalyzed by zirconium acetylacetonate. 2. - Method according to claim 1, characterized in that the allyl methacrylate contains less than 0.02% of atypical alcohol. 3. - Method according to at least one of the preceding claims, characterized in that the weight ratio of atypical alcohol with respect to methacrylic acid ester is in the range of 1: 2.5 to 1: 5. 4. - Method according to at least one of the preceding claims, characterized in that 0.5 to 2 mmol of zirconium acetylacetonate are used per mole of alflic alcohol. 5. - Method according to at least one of the preceding claims, characterized in that the reaction is carried out at a pressure in the range of 500 to 1300 mbar. 6. - Method according to at least one of the preceding claims, characterized in that the reaction is carried out at a temperature of 80oC to 120oC, and the temperature at which the reaction is carried out increases in the course of the reaction. 7. - Method according to claim 5 or 6, characterized in that the temperature is at the beginning of the reaction in the range of 90oc to 100oc, and towards the end of the reaction in the range of 105oc to 115oc. 8. - Method according to at least one of the preceding claims, characterized in that the reaction is carried out in the presence of a polymerization inhibitor, which does not contain nitrogen. 9. - Method according to claim 7 or 8, characterized in that a phenol is used as a polymerization inhibitor. 10. - Method according to at least one of claims 8 or 9, characterized in that a mixture comprising hydroquinone and hydroquinone monomethyl ether is used as the polymerization inhibitor. 11. - Method according to at least one of the preceding claims, characterized in that the fraction of water in allyl methacrylate amounts to a maximum of 0.02%. 12. - Method according to at least one of the preceding claims, characterized in that the reaction takes place under stirring. 13. - Method according to at least one of the preceding claims, characterized in that the reaction is carried out under the introduction of atmospheric oxygen. 14. - Method according to claim 13, characterized in that 0.05 to 0.5 l of air per hour and mole of alplic alcohol are introduced. 15. - Method according to at least one of the preceding claims, characterized in that the alcohol released from the methane acid ester used is separated by distillation. 16. - Method according to claim 15, characterized in that ethanol or methanol is separated. 17. - Method according to claim 15 or 16, characterized in that a mixture containing methyl methacrylate and methanol is separated. 18. - Method according to at least one of claims 15 to 17, characterized in that a part of the separated mixture is introduced into the next load. 19. - Method according to claim 18, characterized in that the feedback fraction of the separated mixture is obtained towards the end of the reaction.